Evidence for a Transverse Single-Spin Asymmetry in Leptoproduction of pi+pi- Pairs

TL;DR

This paper reports the first evidence of a transverse single-spin asymmetry in leptoproduction of pi+pi- pairs, revealing a correlation between target polarization and pion pair orientation, linked to quark transversity and dihadron fragmentation functions.

Contribution

It provides the first experimental evidence of a transverse single-spin asymmetry in dihadron production in semi-inclusive deep-inelastic scattering.

Findings

Evidence of a correlation between target polarization and pion pair azimuthal orientation

First measurement of single-spin asymmetry in dihadron production

Implication for understanding quark transversity and fragmentation functions

Abstract

A single-spin asymmetry was measured in the azimuthal distribution of pi+pi- pairs produced in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target. For the first time, evidence is found for a correlation between the transverse target polarization and the azimuthal orientation of the plane containing the two pions.The corresponding single-spin asymmetry is expected to be related to the product of the little-known quark transversity distribution function and an unknown naive-T-odd chiral-odd dihadron fragmentation function.